Characterization of an Autimycin A resistant cell line of Polytomella Parva

A cell line of Polytomella parva resistant to the metabolic inhibitor antimycin A was isolated. These cells are resistant at a concentration of 2 X 10-5M. Studies on the growth of this resistant cell line (designated P. parva 17-9AA) showed significant changes over that of control cells. Resistant cells in the presence of antimycin have a longer lag phase and generation time than control cells. Resistant cells in antimycin also show an extended stationary phase compared to control cells, and lack the ability to produce cysts. Resistant cells grown in a medium without inhibitor show a decrease in lag time and generation time. Respiration rates were significantly diminished in resistant cells. Resistant cells in the presence of antimycin A respire at a rate approximately 80% that of control cells. Resistant cells show a 1.5 fold increase in specific activity of both succinate and NADH dehydrogenase over control cells. Cytochrome c oxidase activity in resistant cells was 78% that of control values consistent with the notion of a block in the electron transport chain between respiratory complexes I or II and complex III. The specific activity of ATPase in both crude homogenate and mitochondrial fractions was approximately 1.6 times greater in resistant cells compared to control cells. This increase in ATPase activity may provide a mechanism whereby the resistant cell compensates for the inhibition of respiratory complex III by antimycin.

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